I guess the skepticism is just because the only place most of us ever find "perfect" people is when we see them typing from some remote computer online. LOL It might be interesting to follow some of these "New Men" around for a week or so, and see just how perfect their lives really are.
The command is for us to 'be ye therefore perfect', even though we well know we cannot be while in this flesh, because there can only ever be but one Jesus Christ Who was born in the flesh and was perfect, without sin. We are to strive... to be perfect without sin. But like Apostle Paul showed in Romans 7, there is a law in our fleshy members that causes us to sin, even though our inner man delights in the spiritual law of God.
Rom 7:14-25
14 For we know that the law is spiritual: but I am carnal, sold under sin.
15 For that which I do I allow not: for what I would, that do I not; but what I hate, that do I.
16 If then I do that which I would not, I consent unto the law that it is good.
17 Now then it is no more I that do it, but sin that dwelleth in me.
18 For I know that in me (that is, in my flesh,) dwelleth no good thing: for to will is present with me; but how to perform that which is good I find not.
19 For the good that I would I do not: but the evil which I would not, that I do.
20 Now if I do that I would not, it is no more I that do it, but sin that dwelleth in me.
21 I find then a law, that, when I would do good, evil is present with me.
22 For I delight in the law of God after the inward man:
23 But I see another law in my members, warring against the law of my mind, and bringing me into captivity to the law of sin which is in my members.
24 O wretched man that I am! who shall deliver me from the body of this death?
25 I thank God through Jesus Christ our Lord. So then with the mind I myself serve the law of God; but with the flesh the law of sin.
KJV
Should we just stop there with that last Rom.7:25 verse and draw conclusions there? NO! Why not? Because it could lead to ignorance in thinking Paul was saying it's OK for our flesh to follow the law of sin even though at the same time we believe on Christ and our inner man follows The Spirit. That is the false state those who reject 1 John 1 and Luke 11 are in. Since they have believed on Jesus, they turn a blind eye to the continuing sins in the flesh, and say that is Christ's redemption. It is not!
Paul continues the subject in Romans 8...
Rom 8:1-8
8:1 There is therefore now no condemnation to them which are in Christ Jesus, who walk not after the flesh, but after the Spirit.
2 For the law of the Spirit of life in Christ Jesus hath made me free from the law of sin and death.
3 For what the law could not do, in that it was weak through the flesh, God sending His Own Son in the likeness of sinful flesh, and for sin, condemned sin in the flesh:
4 That the righteousness of the law might be fulfilled in us, who walk not after the flesh, but after the Spirit.
5 For they that are after the flesh do mind the things of the flesh; but they that are after the Spirit the things of the Spirit.
6 For to be carnally minded is death; but to be spiritually minded is life and peace.
7 Because the carnal mind is enmity against God: for it is not subject to the law of God, neither indeed can be.
8 So then they that are in the flesh cannot please God.
KJV
Sorry folks, but Apostle Paul showed there the SAME CHRISTIAN DOCTRINE that he showed in Galatians 5, which is, that IF... we walk by The Spirit, then we won't be doing the works of the flesh. But IF... we do NOT walk by The Spirit, then we will be doing the works of the flesh instead, and thus NOT walking by The Spirit.
It's simple:
1. don't do works of the flesh = Walk in The Spirit.
2. do works of the flesh = NOT in The Spirit.
If one can't really grasp the full gist of this, here it is. Eventually, YOU... WE... ALL OF US... will no longer have a flesh body. The type body of the future world to come is a "spiritual body" as the NT teaches. This is why Apostle Paul (and other NT authors) contrasted flesh vs. Spirit so sharply. Your flesh body is NOT... the real 'you'. The real 'you' is inside... your flesh body, and it leaves at flesh death, goes back to God Who gave it (like Eccl.12:5-7 shows). You're flesh body is of the earth, of this material world. Your spirit with soul is NOT made of the material matter of this present world.
So when God's Word is comparing differences between flesh and Spirit, it is talking about two different worlds, or dimensions of existence, for example the earthly vs. the heavenly.
The part of us that becomes "a new creature" in Christ Jesus is our spirit, not our flesh. As Paul later says, if through the Spirit we mortify the deeds of the body (flesh), we shall live (eternally).
I cannot put it any more simply than to say, as Christians, we are supposed to be preparing ourselves (our spirit) for the world to come without flesh. A flesh body is of this present world, not the future world when Jesus returns. This is why Paul also said in Romans 6 those who are dead are freed from sin.